Ok, first off I am assuming that Dracula lived in Castlevania with Lisa and Adrian. Right, now I get to my question: where was his room?
As far as I know, the only thing approaching a bedroom we have seen in Castlevania is Olrox's Quarters. I would say Dracula and Lisa lived together, and I would say that Adrian was conceived in a bed. So, where was that bed? And after Adrian was born, where did he sleep? Ok, maybe he slept in a coffin, but I'm sure Dracula and Lisa had a bed.
Sure, there's the throne room. But Dracula, as prince and master, is bound to have private chambers somewhere.
And another thing (yes, Lieutenant Columbo, what is it?) - Castlevania would have been a strange place to grow up in. Either Dracula's undead army would have been milling about all the time, or the castle would be empty (Lisa still alive = no war with humanity = no army). A huge castle like that, home to THREE PEOPLE.
(And I refer to Alucard as Adrian because he hadn't changed his name yet. It was just one big happy Tepes family.)